email

Avoid using "Noted." As noted in the comments, "noted" should be used only when (a) you are acknowledging that you understand what the speaker said, (b) no immediate action is required from you (although action may be recommended), and (c) you are speaking formally but to someone of equal or lower "rank." Compare with how the word "Roger" is used in the military to acknowledge a command. If a subordinate responds with "Roger," he/she is saying, "OK, I understand what you are saying, and I will comply." It is short but complete and respectful. "Noted" doesn't carry the same depth of meaning and is less polite.

If you are able to go more or less immediately, I would go right then, and avoid the need to reply to the email at all. That is the short answer, and the one I would lead with if this question were on the Workplace Stack Exchange.

But you asked about how to respond "politely" (and presumably via email specifically). Since the email was short, your reply can be short. Your choices are some combination of one or more of the following:

I'll list some examples, but please keep in mind that it really depends on using the right tone that feels comfortable coming from you and is comfortable in the context of your relationships with your professor.

On my way. Talk to you in a minute.

No problem. I'll see you at your next office hours.

Sounds good. I'll be there no later than 3pm.

Of course. See you soon.

I have class until 3pm; I will swing by immediately after.

I'll be there. Would 3pm work for you?

I'm out of town all day today. Would you mind if I came by around noon tomorrow?